This invention relates to overcoming a limitation of the commonly assigned prior art rotary seals of U.S. Pat. Nos. 5,230,520, 5,738,358, and 6,120,036. When such rotary seals are used in devices such as that shown in U.S. Pat. No. 5,979,865, wherein a plurality of rotary seals define a plurality of fluid communication passages between a seal carrier and a relatively rotatable member, at least one of the rotary seals is subject to pressure acting from either side, depending upon which of the fluid communication passages are pressurized at any given time.
The above-referenced prior art rotary seals are generally circular in configuration, and are compressed between the relatively rotatable member and an annular seal groove of the seal carrier. Such seals incorporate a dynamic sealing lip having a generally circular dynamic sealing surface for establishing sealing relation with the relatively rotatable member. The dynamic sealing surface has a circular edge at one side thereof for exclusion purposes and has a wavy edge at the opposite side thereof for hydrodynamically wedging a lubricating film into the dynamic sealing interface between the dynamic sealing surface and the relatively rotatable member.
The prior art seals are best suited for applications in which fluid pressure at the wavy edge of the dynamic sealing surface is either higher than, or substantially balanced with, the fluid pressure at the circular edge. When the fluid pressure of the wavy edge is higher than the fluid pressure at the circular edge, the dynamic sealing lip is supported by the seal groove in a manner that resists pressure-induced distortion of the seal, and the hydrodynamic wedging function of the wavy edge remains unimpaired. When the fluid pressure at the circular edge of the dynamic sealing surface is significantly higher than the fluid pressure at the wavy edge, the dynamic sealing lip is not well supported by the seal groove and severe pressure-induced distortion of the seal can impair the hydrodynamic wedging function of the wavy edge, and can also increase the breakout and running torque of the seal, and increase wear of the seal and the mating relatively rotatable member.
Many applications, such as (but not limited to) the rotary device shown in U.S. Pat. No. 5,979,865, would benefit significantly from a rotary seal that provides low breakout and running torque when subjected to a high differential pressure acting from either side.
The objective of the present invention is to provide a simple and compact, low torque, wear resistant high pressure compression or interference-type rotary seal for applications where the seal may be exposed to relatively high differential pressure acting from either side. The invention also relates to and encompasses rotating machinery such as top drive hydraulic rotary actuators and rotating unions/couplings/swivels wherein rotary seals are used as partitions defining two or more hydraulic circuits.
Briefly, the principles of the present invention are achieved by a hydrodynamic seal for location within an annular seal gland and subject to lubricating fluid pressure for hydrodynamically lubricated sealing with a relatively rotatable surface and for accommodating conditions of lubricant pressure reversal. The seal, in its simplest form has an annular seal body having a primary sealing geometry having angulated tilting surfaces which are merged at the intersection thereof by a blending/pivoting geometry located intermediate opposed flanks of the seal. The blending geometry and its relationship with the angulated tilting surfaces defines a pivotal characteristic with respect to the relatively rotatable surface enabling the annular seal body to be pivotally moved to a first position within the annular seal gland responsive to lubricant pressure from one direction and to establish hydrodynamic sealing with the relatively rotatable surface. The blending/pivoting geometry and its relationship with the angulated tilting surfaces also enables the annular seal body to be pivotally moved to a second position within the annular seal gland responsive to lubricant pressure from the opposite direction and to establish hydrodynamic sealing with the relatively rotatable surface. The seal of the present invention is capable of functioning as a seal for hydrodynamic sealing engagement with an outer cylindrical surface, such as a shaft surface, an inner cylindrical surface, such as an internal housing surface or a planar sealing surface, such as the shoulder surface of a rotatable shaft of housing or the end surface of a rotating member.
At both the first and second positions within the annular seal gland the respective sealing geometry in sealing engagement with the relatively rotatable surface can define a substantially circular non-hydrodynamic edge at the low pressure side thereof and an non-circular hydrodynamic edge at the high pressure side thereof. The blending/pivoting geometry and the angulated tilting surfaces cooperatively define a hydrodynamic geometry for contact with the relatively rotatable surface regardless of the position of the seal with the seal gland.
The annular seal body is also capable of establishing a substantially neutral position within the seal gland when lubricant pressure from either direction is below a predetermined level, with the blending/pivoting geometry the angulated tilting surfaces establishing hydrodynamic geometry at their engagement with the relatively rotatable surface. The annular seal body is capable of rolling movement within the annular seal gland, being rolled to the first or second positions or to the neutral position by the force of differential pressure acting thereon.
The opposed flanks of said annular seal body define annular flank surfaces preferred to be disposed in angulated relation with one another and rendering said annular seal body more susceptible to rolling/pivoting movement within the annular seal gland responsive to reversal of differential pressure acting on said annular seal body.
Preferably the annular seal body is of dual material construction having an energizing section composed of a resilient material having a predetermined range of durometer hardness and having an extrusion resistant section composed of a different material having a range of higher durometer hardness to minimize the potential for pressure extrusion thereof into the extrusion gap that typically exists between the relatively rotatable surface and the structure that houses the seal. Extrusion resistance of the seal is also enhanced by flank corner treatment or geometry which is designed to accommodate the pressure conditions and the fluid characteristics.
The annular seal body may also be provided with lubricating characteristics, such as lubricating projections, lubricating pools and lubricating recesses which are located on the annular tilting surfaces of the primary dynamic sealing geometry and which contain or accumulate quantities of lubricant or direct lubricant migration within the dynamic sealing interface of the seal with the relatively rotatable surface.
The annular seal body may also define a sliding or secondary sealing geometry for static sealing with a surface of the annular seal gland and which slides with respect to the annular seal gland during pressure responsive movement of said annular seal body between its pressure responsive positions. The secondary sealing geometry defines angulated sliding surfaces located in generally opposed relation with the primary sealing geometry and with annular blending geometry merging the annular angulated sliding surfaces substantially intermediate said side flanks of the seal. The annular blending geometry preferably has varying location with respect to the angulated sliding geometry and defines at least one varying edge or wave for hydrodynamic sealing engagement with the relatively rotatable surface. Under circumstances where friction conditions cause the seal to spin within the seal gland the secondary sealing geometry establishes hydrodynamic lubrication at the sealing interface thereof with a gland surface and thus minimizes the potential for heat build-up or unusual seal wear due to this circumstance.